Date post: | 20-Dec-2015 |
Category: |
Documents |
View: | 217 times |
Download: | 3 times |
2003
Birth and Dynamics of Galactic Black Holes
• Demography of quiescent black holes in the present-day universe
• Demography of accreting black holes (quasars) at early cosmic times
• Dynamics of black holes in galactic centers: Brownian motion, binaries
• Effects of quasars on their cosmic habitat
Collaborators: Rennan Barkana, Volker Bromm, Pinaki Chatterjee, . . Lars Hernquist, Stuart Wyithe
The Black Hole in the Galactic Center: SgrA*
VLT with Adaptive Optics
•“3-color”: 1.5 - 3 um
• 8.2 m VLT telescope
• CONICA (IR camera)
• NAOS (adaptive optics)
• 60 mas resolution
Stellar Positions & Motions
Reid et al. 2002
SgrA* in July 1995
Where was Sgr A* in May‘02?
• Sgr A* position: 10 mas
• Star “S2”
seen at pericenter
V ~ 5000 km/s !
Orbit determined
S2’s orbit
• 15 year period
• e = 0.87
• Pericenter
15 mas = 120 AU . = 17 light-hours
(Schoedel et al 2002)
Simultaneous fit of orbits implies:
1. BH mass:
2. BH proper motion: < 0.8+-0.7 mas/yr
(4æ0:3) â (d=8kpc)3 â 106M ì
Ghez et al. 2003
SO-16 closest approach at 90 AU
Feeding SgrA* with Stellar Winds
Loeb, astro-ph/0311512
J < J max = ñ c4GM ï
ð ñEmission region:Emission region:
Sgr A*’s motion
• Continues along Galactic Plane
• Remove Sun’s motion
V(Sgr A*) < 7 km/s
Reid et al. (2002)
Lower Limit on Sgr A*’s Mass
• Backer & Sramek (1999): MV2 ~ mv2 <energy>• Reid et al (1999): MV ~ mv <momentum>• Chatterjee, Hernquist & Loeb (2002)
mass estimator: <energy>
Mlim ~ G M(R) m / R V2
• V < 2 km/s M > 106 Msun
Apparent Deviations from Keplerian Orbits
Loeb 2003 (astro-ph/0309716)
dtobs = (1+ vk=c)dt
a? ;obs = dt2obs
d2x? = (1à c2vk)a? à c
v? ak
Doppler transformation of time:
BH
star
cv ø 10à 2 at ø 100A:U:
Probing the Spacetime Around SgrA* with Pulsars
• BH spin vector from frame-dragging + imaging of pulsar orbit• Inner stellar cluster from gravitational scattering events• Test accretion flow models by measuring plasma density
Pfahl & Loeb 2003 (astro-ph/0309744)
~10-100 massive stars with P<100 yr and lifetime of ~ 107 years~1000 NS in steady state 1-10 detectable pulsars at 10-20 GHz
Enclosed Mass
Schoedel et al. 2002
Water Masers: NGC 4258
Moran, Greenhill, & Herrnstein (2000)
Keplerian Velocity Profile
Miyoshi et al. 1995
Mass densities
Object Density Method
(Msun/pc3)
M 87 2 x 106 HST: 3x109 Msun in 7 pc
NGC 4258 7 x 109 VLBA : H2O 3x107 Msun in 0.1 pc
Sgr A* 8 x 1015 S16’s orbit 3x106 Msun in 90 AU
Sgr A* 2 x 1021 Sgr A*s p.m. 1x106 Msun in 1 AU
SMBH 5 x 1025 Rsch 3x106 Msun in 0.05 AU
Correlation between black hole mass and velocity dispersion of host stellar system
Tremaine et al. 2002
ì = 4:02æ0:32;ë = 8:13æ0:06
ì = 4:02æ0:32;ë = 8:13æ0:06
ë = 8:22æ0:07
ì = 4:58æ0:52
Ferrarese 2002
log(M=M ì ) = ë + ì log(û?=200km=s)
Quasars Reside in Galaxies
Archeology of the Universe
The more distant a source is, the more time it takes for its light to reach us. Hence the light must have been emitted when the universe was younger. By looking at distant sources we can trace the history of the universe.
distanceEarth
Quasars already exist at z~6, only a billion years after the big bang!
Becker et al. 2001
The Earliest Quasar Detected: z=6.43
Fan et al. 2002
Cosmological Infall Around Quasars at z>6
Barkana & Loeb, Nature, 2003
M BH = 108M ì
ð
300km=sVC
ñ5
Ly Line of Quasars
Quasar spectrumSDSS (Vanden Berk et al. 2001)HST (Telfer et al. 2002)ROSAT (Yuan et al. 1998)
Ferrarese et al. 2002Tremaine et al. 2002Wyithe & Loeb 2002
4:6â 108M ì
1:9â 109M ì
2:5â 1012M ì
4:0â 1012M ì
z = 4:80
z = 6:28
M BH =
M BH =
M =
M =
SDSS 1122à 0229
SDSS 1030+ 0524
SDSS 1122à 0229
SDSS 1030+ 0524
SDSS 1122à 0229
SDSS 1030+ 0524
Basic Facts About the Universe• On large scales our universe is simple:
HOMOGENEOUS HOMOGENEOUS: the same everywhere
ISOTROPIC: the same in all directions
Observer 1
Observer 2
Observer 3
Earth
Direction 2Direction1
Direction 3
But on small scales the universe is clumpy
Mean Density
Early times
Intermediate times
Late times
Formation of Massive Black Holes in the First Galaxies
Add Bromm
Low-spin systems: Eisenstein & Loeb 1995
Numerical simulations: Bromm & Loeb 2002
R < 1pc
M 1 ø 2:2â 106M ì
M 2 ø 3:1â 106M ì
õ = 0:05
H2 suppressed
Eddington Limit
For a spherical geometry, the outward radiation force balances the inward gravitational force at the Eddington luminosity:
Gravitational force per proton:
Radiation force per electron:
Accretion of fuel is possible only if
accretion
gasBH
GMmp=r2
(L=4ùr2c)ûT
L E = (4ùGMmpc=ûT) = 1:4â 1046(M=108M ì )erg=s
L < L E
Self-regulation of Supermassive Black Hole Growth
quasar
! 108M ì
M bh = 1:5 200km=sû
ð ñ5
Ltdyn ø 23M gasû2
dynamical time of galactic disk maxf Lg = L E / M bh
halo velocity dispersion
After translating û ! û? this relation matches the observed correlation in nearby galaxies (Tremaine et al. 2002; Ferarrese & Merritt 2002)
M à ûã
Silk &Rees 1998; Wyithe & Loeb 2003
Quasar Luminosity Function
Wyithe & Loeb 2002
Simple physical model:
*Each galaxy merger leads to a bright quasar phase during which the black hole grows to a mass and shines at the Eddington limit. The duration of this bright phase is proportional to the (smaller than unity) mass ratio in the merger.
*Merger rate: based on the extended Press-Schechter model in a LCDM cosmology.
duty cycle ~10 Myr
M ï / v5c
Did the most massive galaxies form at z>6,only a billion years after the Big-Bang?
Core of CDM halos stabilizes at z~6
Stars=collisionless fluid
Loeb & Peebles 2002
late accretion
Proposal confirmed by N-body simulations
Gao Liang & Simon White
(2003) Loeb & Peebles 2002
Brownian Motion of a Massive Black Hole in a Stellar System
Chatterjee, Hernquist, & Loeb 2001 (ApJ, PRL)
For a non-Maxwellian distribution function of stars the black hole is not in strict equipartition
Black Hole Binaries due to Galaxy Mergers
X-ray Image of a binary black hole system in NGC 6240
Komossa et al. 2002
z=0.025
10kpc
Dynamics of black hole binaries
Chatterjee, Hernquist, & Loeb 2002
Figure1.ps
Typical binaries coalesce in less than 10 Gyr due to wandering
Numerical experiment:
400,000 stars
M/M*=0.25%
R
Open issue: kick velocity
Laser Interferometer Space Antenna
Gravitational Wave Amplitude from a Black Hole Binary at z=1
Gravitational Radiation from Coalescence of Massive Black Hole Binaries
Wyithe & Loeb 2002
LISA
PULSARS
REDSHIFT FREQUENCY (Hz)
Environmental Effects of Quasars
Radiative: ionization of intergalactic hydrogen and helium
Hydrodynamic: powerful relativistic outflows
Spectrum of a High Redshift Quasar (z=5.73)
Djorgovski et al. 2001, ApJL, submitted
Transmitted flux ---> HI/HII<1e-6 (Fan et al. 2000)
Djorgovski et al. 2001
On the Threshold of the Reionization Epoch
Structure Formation in the IGM
Density contrast of gas shocked between z=0.14-0.09
Density contrast of gas at z=0 for a 100x100x10 Mpc^3 slice
Evolutionary Stages of Reionization
• Pre-overlap
• Overlap
• Post-overlap
neutral H
Ionized H
Reionization Histories of H, He
Free Parameters: (i) transition redshift, z_tran, above which the stellar IMF is dominated by massive, zero-metallicity stars; (ii) the product of the star formation efficiency and the escape fraction of ionizing photons in galaxies, .
Wyithe & Loeb 2002
H+
He+
He++
Quasar model fits luminosity function data up to z=6
ztran
f escf ?
FILLING FRACTION
REDSHIFT
Quasars as Perturbers:Impact of Quasar Outflows on the IGM
Furlanetto & Loeb 2001
Intergalactic Medium (IGM)
Is the IGM fully magnetized just like the ISM?
jetBAL outflow
quasar
small-scale structure; magnetization; ionization
Magnetized bubble
Volume Filling Factor of Quasar Bubbles
Magnetic energy density normalized by thermal at 10^4 K
Volume filling factor of IGM
Probability Distribution of Bubble Magnetic Field
*Could account for intra-cluster and galactic fields through adiabatic compression. Explains synchrotron halos of clusters.
B / ú2=3
Injection of Positrons from AGN Jets
Furlanetto& Loeb 2002
AGN
e+e- jet
Spectrum of Positron Annihilation Line3-photon decay of Positronium does not smear line due to keV temperature of cluster electrons (direct annihilation more probable)
Line signal detectable with INTEGRAL (launched Oct. 2002) and EXIST (space station) for rich X-ray clusters out to 100 Mpc
More details: ApJ, 572, 796 (2002)
What fraction of the earliest quasars is being gravitationally lensed?
Barkana & Loeb 2000
OCDM
LCDM
SCDM
- PS Halos
- -No evolution
Are the Highest-Redshift Quasars Gravitationally Lensed?
Wyithe & Loeb, Nature 2002
4 SDSS Quasars with z>5.73
QuasarObserver Lensing Galaxy
Excess magnification due to stars next to one of the images
Time Delay = (gravitational +geometric)
Magnifying the Broad Line Region of Quasars with Stellar Microlenses
Quasar accretion disk
(source of continuum emission)Wyithe & Loeb 2002
Observed Time-Delay Lightcurves
RX J0911+05
SBS 1520+530
Burud et al. 2002
Anomalies of Time-Delay Lightcurves
Observations: up to a few percent variations on tens to hundreds of days
Observed anomalies in RX J0911+05 & SBS 1520+530 by Burud et al. (2002) ---> N<10^6
Lack of anomalies in Q2237+0305 ---> N>10^4
Inferred cloud number is consistent with bloated star model (Alexander & Netzer 1997)
The Future of the Intergalactic MediumÒË = 0:7;Òm = 0:3
(Recombination time)>>(Hubble time) outside collapsed objects today. This inequality will get much stronger in the future because the IGM density will be diluted exponentially with cosmic time.
Future Evolution of Nearby Large-Scale Structure
Nagamine & Loeb 2002
Coma
Great Attractor Perseus
Pisces
The Long Term Future of Extragalactic Astronomy
Loeb 2002, PRD; astro-ph/0107568
us
c
Accelerating
source
AnalogyAnts = Photons Balloon=Expanding Space
AnalogyAnts = Photons Balloon=Expanding Space
visited area (horizon) since blowing started (Big Bang)
AnalogyAnts = Photons Balloon=Expanding Space
visited area (horizon) since the blowing began (Big Bang)
Ants can be separated at a rate much larger than their own walking speed
Maximum Visible Age
All sources above a redshift of 1.8 are already out of causal contact with us!
How many galaxes will reside within our event horizon in 100 billion years?
Answer: one
(the merger product of the Andromeda and Milky-Way galaxies)
Ejection of Stelar Mass Black Holes from Globular Clusters
star-star
star-BH
BH-BH ejection Chatterjee, Loeb & Haernquist 2003
Bright quasars reside in massive galaxies: Spectral Signature of Cosmological Infall Around the First Quasars
Barkana & Loeb, Nature, 2003; astro-ph/0209515
infallaccretion shock
virialized gas
observer
redshiftedaccretion shock
Simulation of Reionization
log(f_HI)
Ionizing - Background
log(gas density)
log TGnedin (2000)
z=11.5
z=7 z=4.9
For comprehensive reviews on Reionization, see: *Barkana & Loeb 2001, Physics Reports 349, 125*Loeb & Barkana 2001, ARA&A, 39 (Sep. 15)
1-sigma 2-sigma 3-sigma
Atomic cooling
H_2 cooling
2-sigma
Collapse Redshift of Halos
Probability Distribution of Bubble Radius
*Magnetic pressure larger minimum b-parameter of Lya forest
Redshift and Splitting Distributions of Lenses
- LCDM
- - OCDM
… SCDM
z_s=5
z_s=10
z_s=2
z_s=5 z_s=10
Flux from Lensing Galaxy in G-P Trough
z_s~6
I*=22.2
23.322.2
SDSS at z=6.28
Alternative Interpretations of Lightcurve Anomalies
Hot spots in accretion disk
Black Hole
(Gould & Miralda-Escude 1997)
Hotspots: timescales are too short compared to observations!
Second Alternative:Microlensing by Planets
Accretion disk
Motion in 10 years with a transverse velocity of 400 km/s
(Schild 1996)
Planets: timescales are too long!(Also, ruled out by the MACHO search).
ü/ ú2R2
/ (1+ z)4
Absorption Spectrum
Spectrum of a Source Just Beyond the Reionization Redshift
A Simple Explanation
Explain: binding enrgy per dynamical time
Laser Interferometer Space Antenna (LISA)
Future Prospects
• Vlim ~ 1/t3/2
• Mlim ~ 1/V2lim <energy>
~ t3
• When Vlim ~ 2 km/s (~2007),
Mlim ~ 106 Msun
• Could show ALL mass in Sgr A* !Reid 2002